As the data rates of computers, telecommunication, etc. arm ever increasing, optical communication, well established since long times in long distance broad band communications, is also being introduced for short range applications inside exchanges and computers, etc. For such applications the number of optical interconnections may become significant. Thus there exist a need for controlling and handling the routing of optical fibers or generally optical wave guides.
One practical approach to his is to use a separate optical level to house all the optical connections in the shape of an optical flexfoil having internal fibers or waveguides. By using optical connectors at the ends of the fibers/waveguides connections can be established to electro-optical devices and to external devices such as electrical backplanes.
The company AT&T has in a few patents, in particular in U.S. Pat. No. 5,204,925 for Bonnani et al., described the use of optical fiber flexfoils having tabs extending from the man body of the flexfoils and being capable of being twisted in a 90.degree. angle in relation to the main body in order to accomplish an "edge to edge" backplane connection where the edges of the main bodies of the circuit boards and the main bodies of the backplane flexfoils are located perpendicularly to each other. For general systems this is an unusual configuration as compared to the more familiar one where the circuit boards extend perpendicularly from the backplane. However, such a solution could possibly be accomplished in the AT&T solution by folding the flexfoil.
However, the AT&T concept has one severe limitation in that it is not possible to accomplish a connection of an edge of a circuit board at several distinct positions to the backplane using the simple geometrical solution disclosed. By having further prolonged tabs which both can be both twisted and bent, such connections would in principle be possible but the edge length of the backplane foil from which the tabs extend would be much larger than the otherwise required separation between or spacing of the boards, this effect being even more pronounced in the case where more tabs are required per circuit board.
In U.S. Pat. No. 5,259,051 for Burack et al., also assigned to AT&T, a method of making an optical flexfoil is disclosed. In the embodiment described in conjunction with FIG. 7, a base foil is used having tabs extending from a main body of the foil. On this foil one or more optical fibers are routed and then cut and thereupon possibly, a top foil can be applied. Finally the tab edges and the border are cut.